Electrical musical instrument



April 26,1949. J. M. HANERT ELECTRICAL MUSICAL INSTRUMENT Filed Dec. 23, 1944 4 Sheets-Sheet l ll/Gf/EST NOTE. OSC/LLATOR LON/57 #07: OJC/LLATbR .f/Pvenfo7 April 949. J. M. HANERT ELECTRICAL MUSICAL INSTRUMENT Filed Dec. 23, 1944 4 Sheets-Sheet 2 5/679 F/RST DIV/DEE 57/765 R R M w 0 N 0 7 x 7 V9 2 a 4 7 70 c m R 6 m a 6 U M m 5 0 N m M A r m a 4 W s H a cm 5 .Mh H 3 m a K H w 7 u R 7 0 F an n FIRST DIV/DEE STAGE F012 Lon 57 NOTE (/9 April 2 1949.

J. M. HANERT ELECTRICAL MUS ICAL INSTRUMENT John MES/n92" z Patented Apr. 26, 194-9 ELECTRICAL MUSKCAL INSTRUMENT John Hanert, Park Ridge, 111., assignor to Hammond Instrument Company, Chicago, 111., a corporation of Delaware Application December 23, 1944, Serial No. 569,568

7 Claims.

My invention relates generally to electrical musical instruments and more particularly to improvements in instruments for producing the bass tones of instruments of the organ type.

2 of the frequencies of its conttrolling oscillator, These alternate pulse frequency divider stages operate to divide the input frequency by a factor of two, substantially irrespective of It is y the t nensive and elaborate pipe any variation in frequency of the input signal. O s Which h e a quate pedal steps. This is The output signal of each of the divider stages due primarily to the fact that the pipes for prois in the form of a rectangular or box wave and ducing bass tones are necessarily Very larg ethis output signal is thereafter modified to proquire a large amount 91 air ca s them duce three different types of signal waves which il eak, and arei thus initial y Gripe effenslve are utilized for tone production. One of these 0 Opera 6,911 reqllll'e ilrge cilamioers- 5 a modified signal waves is in the form of sharp S 2W p p 0138115 3 m e than W79 three impulse negative peaks, representing a relatively i t l Pg P 13 g? i l g 1 5 bright reed-like tone quality. The second is in ass P are usual 3 S W 1 C the form of relativel smooth ne ative ulscs re due to the time required for the building up of the resenting a musicalytone having a diallasomlifie acoustic wave trains in the pipes. If it were attsne quality. The third is in the form f a Slightly i fil az n ti gi lififii 51 1: 31 l rt lieg igi z iodiiied sine wave, representing a musical tone to, the q ality oi the tones emitted. by the pipes gjgg e r l gi i o f re giii s i i gh 1 3 would be undesirably altered and the pitch of the thre are but few Odd harmonics of lesser tones would not be steady. Furthermore a much phtuda larger capfcity w would i f l q 4 By means of the stop tablets the desired type of g fi gggjfgfi gg f g gg f pfg agga}; output signal of the various divider stages are seare remedied by the provision of electronic means iig g h g g fi 1 ,11 ,12 g i ig g zfiggfig fig for generatin and contrcllin tones in the lower meht' The signals of the first mentioned type, :2: 5 35 z i g i i fi that is, those appearing as a series of relatively utilized es a supplement the eto ma iin; of sharp newt-iv? impulses are transmitted through the conventional sto tablets and relays of the phase shlftmg petwork whereby the relative in; or an phases of the partials of the tone are changed to u g the rivnar event 0 V want; t reduce the peak amplitude of the signal and thus rovida v1 imbgoved i l l t f gf facilitate distortionless transmission of the sig- S 6 f mgans use ggg 'fg nal through the amplifying and speaker system.

'3. I I l with a pipe Organ or as asunplement to Other This phase shnting networl; eliminates the maawcpi and 01 e l musical instruments chlne gun effect which would otherwise be pro- Other objects will appear from the following gfigi i g 3i$2 g relatlvely Sham lmpulses description, reference being had to the accompanying drawings in which: p' OI the phase shifiomg network 15 Figures 1, la, 1b and 10 together constitute a 40 ifis gggj 3 ffg i g gg z E schematic wiring diagram of the improved instrup mp an O ment. and plitude controlled by a pair of push pull control Figure 2 is a Wiring diagram of a modified form gem-Odes 5 Concrol g are t normally of generating and switching apparatus iased so as o e non-con uc mg bu are renp D S dered conducting by the closing of a contact \XENERAL E CRZPTION upon energization of any one of the pedal con- In general, the instrument of the invention trolled relays. The amplitude controlled signal is comprises a source of relativeiy high frequen ies supplied to a power amplifier which is coupled of the tempered musical scale, disclosed herein as to a speaker, t e latte 10 Preferably located a. pair of oscillators which are respectively tuned in the organ swell box so as to have the sound to frequencies related to those represented by the output thereof controlled in part by the usual highest and lowest depressed pedals of the organ swell shutters. pedal clavier. Each of these oscillators is pm- It will be understood there is a system as above vided with a cascaded alternate impulse freescriced for each of the oscillators, the only quency dividing system whereby there may he means common to the two systems being the congenerated frequencies A and tacts under the pedal controlled relays, by which the biasing potential on the control tubes of both instruments is determined.

In Fig. l are shown representative pedals of a pedal clavier including pedals CG, Gil, Alt and.

The relays M are provided, instead oi=having thepedals directly actuate the relay switches, in order to facilitate the installation of. the apparatus in a pipe organ, since the conventional pipe organ has the switch contacts It for. controlling relays it. These relays are rendered relatively'slow-acting by theprovisionsof antispark -resistors-R:l 5 in-parallel with the windings thereof;

Each-of the relays M operates single pole double. throw'switches l6 and- H and shortly thereafter. operates-2a. single pole single throw switch. l8. This is .accomplishedin the usual manner. by haVingthe contacts vfor switch it initially spaced farther apart than ar the contacts for. switches ldandi H,..or by equivalent armaturestructure whereby the armature will closeswitchesiti andJl. before it closesswitch l8. Switches. ,Hiuand ll control the tuning of a pair of oscillators Elliand 2 iv respectively for generating frequencies having a definite relationship, respectively, withtlie frequency represented by the higliest'note pedal depressed and'the frequency represented by. the lowest note pedal. depressed. Each of'the oscillators comprises a triode tZ lhaV- ing a cathode"25,'.contro1 grid'zt and anode 28.

The tuning circuit for the oscillator comprises mutually. coupled vinductances Ltd and L32," the iriductanceLiiZ being connected; between the cathode" 25 and ground, while'the'inductan'ce L363" has a plurality oftaps' corresponding in" number to one less than the usual :32 pedals. Depending upon: which of" th switches I6 is operated a greater 'or'lesser' number of 'turns'of L3 il-areconnectedf betweenground' and'the' grid .2 6, this connection"being through a grid resistor RS -thy pass'ed' 'by' a" capacitor Citfi. The capacitance portion of the tuning'circuit' includes a capacitor C33-and-a trimming capacitor G 'iil. Overall tuningof'the range of'the oscillator Zilis accm-- plishedby adjustment of th air gap in the core common to the'inductances L3G and L32.

-"Pla-te current for the triode 2 8 13 supplied from a suitable source, indicated as a battery 42, througha plate load resistor RM;- and the signal output of the oscillator is iIllD-X'BSEGd-UDOH the grid-- lfi 'of' a triode 28 through a blocking condenser C58; The grid iteis connectecl to aplate' current cutofi-negativebias potential source; indicated as C;-through'a grid resistor R52, :whileithe cathode-be et this triodeds connected to ground. The.-

It will be noted that the connections of the switches it are such that when the relay Hi for the highest note pedal is operated, the remaining switches l are disconnected from the circuit while the operated switch i6 efiects connection into the tuning circuit of a predetermined number of turns of L36 so as to cause the oscillator to operate at a frequency which bears a definite relationship to the nominal-frequency of the pedal which has been depressed.

On the other hand, it will be noted that the switches ll for the oscillator 2! are connected in such manner that the lowest depressed pedal will tune the oscillator 21 to a frequency bearing a defi'niterelationship to the depressed pedal, while switches ll associated with pedals higher than that depressed. This type of switching system andzxosoillator tuning means are more fully disclosed in the patent to Laurens Hammond et al. No. 2,332,076.

Alternate impulse frequencydioider Stages The pulses. forming the output of the triode 118 are. transmitted to the first stage of a plurality of. cascaded stages of alternate pulsefrequency dividers. The .fil'st dividerstage comprises triodes lEiand'iLthetriode it including a cathode lllagrid "it and an anode it, while the triode 'll ,includes a cathode 53, a grid is and an anode ll;

Sharply peaked negative pulses constituting the output of thetriode as are simultaneously linpressed .upon grids lit and 15 through a pair of small capacitors CW and CH9, these grids being connected to ground throughresistors Pei-3e and REE. respectively. The plate ll is connected to a suitableisource of plate current, indicated as a terminal-+300 v. of the power supply, through a plate load resistor R83 while they plate i6 is connected to the +300 v. terminal through a load resistor RM.

The plate I? is coupled to the grid it through a feedback mesh comprising a resistance R9 5 which is shunted by a capacitor CQB, the latter being in series with a resistor 'Rilll. Ina similar manner. a mesh comprising resistors R38, Riilll and capacitor 0% provides a feedback circuit from theplate it to thegrid T5.

The output of the triode H is supplied to the grid 35 of a rectifying triode see through a blocking capacitor Ciel. The grid I0? is negatively biased through a resistor Rlilii' which is connected to. a suitable negative terminal of the power supply, indicatedas C. The cathode of triode l teis connected to ground through a signal derivation resistor Ri m which has a filter capacitopin parallel therewith. It will. be apparent that potential of the cathode H4 will be of a wave form comprising a plurality of relatively sharp positive peak impulses. Such impulses are utilized as one of the output signals of the first divider stage, such signal being transmitted through a conductor H6. This signal is very bright in ton quality, such as is characteristic of the reed and trombone families.

A second type of tone quality signal is also derived from the output of the first divider stage. A triode I l8.has its grid i211 connected by a conductor I22 and a blocking capacitor ClZd to the anode; ll of triode 'H. The anode I26 of triode ll81-is connected to asuitable potential source, indicated as +B, while the grid I20 is connected to..a .negative potential biasing, source, indicated as -0, through; aresistorRlZB. The'cathode' I30; ofitriode H8-is connected to ground through a capacitor 0 I34 connected in parallel therewith, and the resistor RI32 having a capacitor CI36 connected in parallel with it. The musical tone signal, which is of the diapason quality, is derived from the cathode I36 of the triode through a resistor RI40 and a conductor I42.

A bourdon-like tone quality is derived from the cathode 12 through a conductor I44.

Tone quality selecting means tively for the highest note channel and the lowest note channel. There are three relays 550 for each frequency divider stage of the highest note channel as well as three relays ISI for each divider stage of the lowest note channel. The relay I50a for the first stage of the highest note channel is arranged to connect the conductor I44 to conductor I52, While relays I561) and 1500 are adapted respectively to connect the signal conductors I42 and H6 to a conductor I54. The

relays I 50a, I5Ilb and I580 for the first divider stage will be energized respectively by the closure of stop switches I46 for 1' octave piccolo, 1' octave fifteenth and 1' super-octave clarion. Similarly the corresponding relays for the second divider stage may be energized by closure of the switches I46 of the stops labeled 2' piccolo, 2 fifteenth and 2' octave clarion. The relays for the third divider stage are similarly operated by closure of the switches I46 associated with the tablets for the 4 fiute, 4 octave and 4' clarion. The relays for the fourth divider stage are controlled by the stops identified as the 8 flute, 8' diapason, and 8 tromba. The relays for the fifth divider stage are controlled by the tablets identified as 1.6 bourdon, 16 diapason, and 16' trombone. relays for the sixth divider stage are controlled by tablets indicated as 32 sub-bass, 32 diapason, and 32' bombarde.

The second to sixth divider stages for the highest note are shown in block diagram form is with appropriate legends applied. Three relays I50a, I 50b and I 500 for each of the divider stages for the highest note are conventionally illustrated, while the corresponding relays for the divider stages for the lowest note are indicated as blocks with appropriate legends.

Each of the relays I50a of the different divider stages is adapted to connect the cathode of its associated triode 10 to the conductor I52. Relays I 50b connect the cathodes of their associated rectifier triodes II8 to the signal conductor 554; while the relays I 560 connect the cathodes of the rectifier triodes, such as the triode I96, to the signal conductor I54.

Phase shifting network Since the signals transmitted through the conductor I54 have a wave form constituting a series of relatively high amplitude positive peaks, they are not transmitted efiiciently, in this form,

to a shape in which the highest amplitude peak The 3 is but a fraction of that of the input wave, without appreciably altering the amplitudes of the individual partials. The operation of this phase shifting network is more fully disclosed and claimed in my copending application Serial No. 569,569, filed December 23, 1944.

The coupling between the generating system and the phase shifting network is herein illustrated as being effected by a transformer TI60, the phase shifting network comprising a plurality of sections of series capacitors CI62 and shunt inductances LI64. This phase shifting network terminates in resistors RI66 and RI61 which together form the characteristic terminating impedance for this network. The output of this phase shifting network is impressed upon the grids I10 of push pull preamplifier triodes I12, the connections to the grids being through decoupling resistors RI14 respectively. The cathodes of the triodes I12 are connected to ground through biasing resistor RIlG while the plates of these triodes are connected to the terminals of the primary winding of a. coupling transformer TI18. A center tap on this winding is connected to a suitable source of plate current, indicated as +B.

Output and amplitude control circuits The signal conductor I52 conveys the signals from the cathode of the triode 10, and the similar triodes of the other divider stages, to a decoupling transformer TI80, the output terminals of which are connected respectively through decoupling resistors RIBZ to the grids I10 of the triodes I12.

The terminals of the secondary of transformer T513 are connected respectively to the control grids I84 of remote cut-ofi control pentodes I86, while the center tap of the secondary of transformer TI'It has conductor I88 connected thereto. The conductor I88 is connected to ground through a capacitor Cite and is connected to a suitable source of negative biasing voltage, indicated as 7 v., through a resistor RI92. The cathodes I94 of the control pentodes I86 are connected to a conductor Ids. It will be noted that the conductor 596 is adapted to be connected to ground through resistor RI91 (Fig. l) by one of the switches I8 (Fig. 1) whenever any pedal rela I4 is energized. The conductor tilt is normally maintained at a positive potential by virtue of its connection through a resistor Rltii to a terminal of the power suppl indicated as +300 v. and its connection to ground through a resistor RZfiil shunted by a capacitor C262. Resistors RISE and RZtB form a voltage divider which normally maintains the potential of the cathodes 94 at such positive value that the pentodes I86 are biased beyond cutoff.

The generating system for the lowest note is i in every respect similar to that above described for the highest note and corresponding parts of the generating and signal transmission system for the lowest note have reference characters applied thereto corresponding to those of the similar parts of the highest note generating and signal transmitting system. For the sake of simplicity the phase shifting network and preamplifier for the lowest note are shown as a block 206 havin an output coupling transformer TZtS corresponding to the transformer TI18.

The center tap of the secondary of transformer is connected to the conductor I88 which, it will be recalled, is also connected to the center tap of the secondary of transformer TI1B. This conductor I 83 is adapted to be connected 7 through a rcapacitor Q2 Iii (Fig. 11-0); with the conductor E96 uponclosure, of a relay operated switch 252. Theswitch ztz might also be manually operated and'located at the console.

The control tubes 186 for the highest note transmission system are, suitably coupled to a poweryamplifier 2M while, in a similar manner, the corresponding control tubes '2l3 are suitably coupled to a power amplifier 2E6. The outputs of'the amplifiers 2M and 2E6 are supplied respectively to speakers 215 and 2!? which are preferably located .in a chamber 258 forming the swell box of the pipe organ, or in a similar chamber-in which the sound outputmay be controlledby aplurality of swell shutters 22% formingonesideof the box or chamber. The shutters 220 are controlled from the console of the instrument in-any well known manner, and thus control the acoustic output of the speakers M5 and 2H, as well-as the acoustic output of any organ pipes which may be located in the swell box or chamber.

In addition to controlling-the acoustic output of the instrument by meansof the swell shutters 2 20, initial adjustment of the overall outputof the control tubes 85 and M3 may be obtained by adjustment of adjustable resistors R232 and R233, respectively, for the highest and lowest notes. In lieu of placing speakers 255 and 25? in a swell chamber, separate volume controls of suitable construction, operating upon the potential of one or more of the electrodes of the controltubes I86 and H3, may be used to control the intensity of output of the instrument.

Operation In playing the instrument the organist will operate the pedals in the usual manner. Whenever but one pedal is depressed, both oscillators 20 and ,2i will be tuned to the same frequency, corresponding to sixteen times the fundamental frequency of the pitch represented by an 8 stop of the depressed pedal. When two of the pedals of thepedal clavier are simultaneously depressed, that corresponding to the highest pitch will tune the oscillator 20 to a frequency sixteen times the fundamental of the pitch represented by an 8 -stop of the highest pedal depressed, While the oscillator 2| will correspondingly be tuned to a frequency sixteen times the fundamental of the pitch corresponding to the lowest pedal depressed. The output of each oscillator wil be rectified and have its wave shape altered to produce a relatively sharp negative pulse suitable for the inputof the first frequency divider stage coupled to the oscillator.

In describing the operation of the frequency divider stages it will be assumed that no signal is being supplied thereto by the rectifier triode 48. In this case a static condition prevails in which one or the other of the tubes iii or H is conductive of plate current to an appreciably greater extent than the other. This may be understood by assuming that the potentialon theplate ll is decreased slightly. Such slight change of potential in a negative direction will also appear on the grid 14 of the triode due to its connection with the plate ll through the coupling mesh comprising resistors R91 and RIM and capacitor C99, and will also result in an increase in the potential at the plate '55 of the. triode ill. Such-increase in plate potential will similarly appear at the grid 75 due to its intercoupling with the'plate l6 through the mesh comprising RSG RIOO and 1098. This increase in the positiveness .-of the grid 15 will ;cause a.

further decrease in potential at the P1341 8 511,.

tion will prevail for anindefinite periodoftime because of the direct reciprocal resistance "coupling between the grids and plates of the triodes ill and ii. Due to the symmetry of thecircuits and of the characteristics of the triodes HI-and ii, it becomes a matter of chance as to which of these triodes will conduct maximum plate current in the first instance. As will be :explained hereinafter, it is unimportant to predetermine which of these tubes will initially. conduct the greater plate current.

The speed with which changes inpotentiallat any of the electrodes of these triodes 10, H can occur due to this mutual feedback effect is limited by the shunt capacitance offered by the capacitors C18 and CW and the interelectrode capacitance present in the triodes l0 and H. Bylincluding capacitors C98 and Oils the-efiect-ofihe shunt input capacitance is largely overcome-because there is a direct low impedance connection for very high frequencies between the anode ll of triode H and the'grid 74 of "triodeloand also'between the anode l6 and grid 15. The. inclusion of these capacitors results in a-substantially instantaneous mutual feedback between the triodes, which sudden changemaybe interpreted mathematically as being an extremely steep wave front having a Fourier harmonic 'se-' ries extending up to extremely high frequencies such as radio frequencies. It was found undesirable to permit this wave to contain such high frequencies, because when such was the pass, radio frequency interference and spuriouscouplings were preva1ent,-thus rendering the divider unstable. By inclusion of resistors RIM- and Rllli in series with the capacitors C98 and C98, the rate at which such mutual feedback potential changes can occur is considerably decreased because of the time constant introduced by the resistors REM! and the capacitors ClBgand C119 together with the interelectrode capacitancesof the triodes liland N. This decrease in-the rate of change of potential substantially eliminates harmonic components of the Fourier series which lie appreciably above the super-audio range.

As pointed out heretofore, prior. to the application of a negative pulse-from the rectifier triode 48, one of the triodes ll], ll will baconducting with maximum plate current and the other triode will be at substantially plate current cutoff. The series of short high amplitude megative pulses are simultaneously transmitted to. the grids l4 and i5 through the small capacitors. 0'58 and C19 whenever the oscillator 20 is in operation. Assuming that the triode is drawing maximumplate current and that triode .lliscut off, this simultaneous application of thenegaillive pulse to the grids M and 15 will result in aide.- crease in the plate current of triode .10, thereby causing the potential on the anode .16 to increa e. This positive increase in potentialis transferred from the anodeltto the grid 15 through thefeedback mesh comprising R96, Rifle andQCQSMI n crease in positivenessof the grid 15,in.turn 118- sults in a negative potential change at its plate 11, which negative potential change is similarly transmitted to the grid I4 through the feedback mesh comprising R91, RI Ill and 099. This negative change in grid potential results in a further increase in the potential at the anode I5, which change is in phase with the original positive change at the anode I8 due to the application of the negative pulse on the grid I4 from the rectifier 48. This mutual feedback action continues despite the disappearance of a signal pulse on grids I4 and I5. The action ceases when triode II is at substantial plate current cutoff. Due to the direct resistive coupling of the grids and anodes of the triodes I and II, this cutoff condition will prevail until the rectifier 84 transmits another negative pulse to the grids 14 and I through the capacitors C18 and CI9. By making the time constants of the feedback meshes (comprising R98, R91, C98 and 099) about eight times the time constant of the signal input circuits (comprising R80, RSI, C18 and C19), the duration of the input pulses is made short by comparison with the duration of the pulses produced by the feedback meshes. This insures that the negative signal impulses will have disappeared before the feedback action is completed.

From the foregoing it is apparent that this first negative pulse from the rectifier 84 was effective to transfer the current from the previously conducting triode I0 to the previously cutoff triode I I. When the rectifier triode 48 again supplies a high amplitude negative pulse to the grids I4 and I5, triode III will be caused to draw maximum plate current and triode 'II will again be cut off. Thus it is seen that alternate negative pulses from the rectifier 48 are effective to cause similar changes in potential in the output circuits of the triodes I0 and II and thus the frequency of the plate current of either of these triodes will be one half of the input frequency. The shape of the wave in the plate circuits of triodes I0 and II will be substantially rectangular. The wave shape will differ slightly from a rectangle in that the positive slope is more steep than the negative slope. This is accounted for by the fact that the negative pulse input circuit has a shorter time constant than that of the feedback meshes.

The harmonic analysis of a rectangular Wave shows that it comprises a fundamental of given amplitude plus a third harmonic of one third of the amplitude of the fundamental, a fifth harmonic of one fifth the amplitude of the fundamental etc.

The rate at which the input pulses are supplied is immaterial to the frequency dividing operation. By using relatively small capacitors the frequency range over which these frequency dividers will operate successfully may extend over the entire audio frequency band. In the embodiment of the invention disclosed herein, the divider stages are required to divide over a range of only 32 semitone intervals, slightly more than two and one half octaves, so that no difficulty whatsoever is experienced in having the frequency divider stages consistently and accurately divide their input frequencies by 2. The inclusion of the series resistors RIM and RIIII serves to decouple the input grid circuits from the output feedback meshes, and thus renders the circuit more stable in operation and less sensitive to the exact values of the input capacitors C18 and C19. The resistors RIM and RIIII, together with the feedback meshes comprising C98, C99, R96 and R91 determine the upper frequency limit to which 10 the divider functions in a stable manner. These time constants should be small in comparison with the time required for one cycle of the highest audio frequency (e. g. 1568 c. p. s.) which is to generated by the oscillator 20.

Since the output of the triodes 'II is of generally rectangular wave shape it is necessary to rectify this wave and to change the negative portion of this wave into relatively sharp negative pulses, for reliable operation of the second divider stage. The rectifier triode I which may be considered as part of the first divider stage performs this function as as providing a suitable reed I crms the double function of providing a suitable input signal for the second divider stage as well as providing a tonally suitable output signal for reed and trombone-like tones. A somewhat similar but less bright tone quality is derived from the rectifier triode II8, due to the filtering action of the mesh RI3I, RISE, Rl iu, (JIM and CIS i connected to the cathode I 38 of this triode. The signal derived from the cathode I2 through the conductor I44 is a symmetrical wave having well rounded peaks and troughs, and as previously pointed out, represents tones of the bourdon type, namely tones having a strong fundamental and a relatively weak series of odd harmonics only.

The organist will operate one or more of the stop control switches hit and thereby transmit to the coupling transformers TItQ or TI8Il or both, the desired tone qualities and octave coupler effects. Since the bourdon type tone qualities derived from the cathodes of the triode 10 of the various divider stages is initially of a smoothly undulating character, it is not usually necessary to shift the phases of the partials and therefore these tone signals are transmitted di- 9 reotly to the grids Ilia of the preamplifier triodes.

As previously pointed out, the relatively high peak amplitude pulses derived from the cathodes of the rectifier triodes Hi5 and IEIB would tend to overload the amplifier and speaker system, since these wave forms represent a phase relationship of the partials in which their peak amplitudes coincide. By means of the phase shifting network, the peak amplitudes of the various partials are variously displaced so that the peak amplitude in a single cycle of the fundamental is reduced to approximately one third of the original peak amplitude of the signal, and the machine gun effect is removed.

Whenever one of the pedal control relays I4 energized, it closes its associated switch I8. The grid bias on the remote cutofi control pentodes I86 and 2I3 is normally sufiicient to out off these tubes due to the application of a positive voltage to the cathodes of these pentodes by means of the voltage divider mesh comprising RIQB and R282]. Thus, when one of the switches I8 is closed, it connects the cathodes of these control pentodes I86 and 213 to ground, renderlug these tubes conductive with a prompt attack.

When it is desired to have the intensity envelopes of the signals of such form that the attack is relatively slow, the switch 2I2 (Fig. 1c) is closed, whereupon the lowering of the potentials of the cathodes of the control pentodes I88 and 2I3 is accompanied in the first instance by the corresponding lowering of the potentials on the grids of these control pentodes. However, after a short time, as the capacitor CZIll becomes charged, the grids of these pentodes become increasingly positive with respect to their cathodes, andthey. commence conducting the signals on their grids with gradually increasing amplitude, producing the effect of slow tonal attack. When a pedal is released its relay It operates first to open its switch 18 and immediately thereafter to operate its switches It and IT. The opening of switch [8, by disconnecting the cathodes of the control tubes I86 and MS from ground, permits their potential to rise rapidly to cut-off potential, the rate of potential rise being determined by the values of RISB, R266 and C292. Thus the tone will have decayed substantially to zero intensity by the time that switches l6 and I! are operated to change the frequency of oscillation of the oscillators 2!! and 2|.

Since the apparatus employs conventional organ controls, it may be considered as an integral part of the pipe organ, not requiring the organist to learn any new technique of registration. The only control in the apparatus disclosed herein which could not be accomplished by the usual pipe organ controls is that of producing slow or fast attack at will, by operation of .the switch 212.

While the use of the variable frequency oscillators, whose frequencies are controlled by the lowest and highest depressed pedals has manifold advantages, there are some instances in whichother forms of generators may be coupled tothe divider stages in place of the variable frequency oscillators. For example, in adapting the invention to an electric organ of the type shown in the patent to Laurens Hammond, No. 1,956,350, it would be unnecessary to provide two oscillators, but instead the various frequencies supplied to the frequency divider stages could be. obtained from the phonic wheel generators present in this type of organ. A circuit suitable forutilization of such generators as the sources of the various frequencies required is shown in Fig. 2, in which figure circuit elements corresponding to those previously described bear corresponding reference characters.

In Fig. 2 the pedal energized relays operate single pole double throw switches it for selecting the generator related to the pitch of the highest pedal depressed and single pole double throw switches Ill for selecting the generator related to the pitch of the lowest pedal depressed. In this figure the generators 290 are utilized as the frequency sources. The three generators 2% conventionally illustrated are representative of the 32 semitone generators which would be utilized forsupplying the frequencies for the 32 pedal notes. These generators will generate frequencies at the various semitone intervals from 523.25 0. p. s. to 3135.96 0. p. s. The generators 2% are respectively coupled to the upper contacts of switches I6 and ill through resistors R292. Switches l6 are so connected in series that operation of any switch it renders ineffective the switches It oflower pitch, and thus the switches l6 control the transmission to the output conductor 294 of a frequency related to the highest depressed pedal. The switches ll are connected inseries in an opposite manner so that the lowestpitch switch ll which is operated determines which of the generators 290 shall be connected to the .output conductor 2%. The output conductor 294 transmits a signal through capacitor C50 to the pulse sharpening and rectifying triode 48 preyiously described, and this pulse is then utilize r controlling the frequency of operation of the cascaded alternate pulse frequency divider stages, all in the manner previously described.

By utilizing the frequency generating system of Fig. 2 a reduction in the cost of the instrument may be effected in some instances, especially;

those in which the generators 2% form a rogue This system also quencies produced by the generators 298. There.

will thus be no possibility of beating of the harmonies of the pedal tones with the frequencies derived directly from the generators 290.

While I have shown and described particular embodiments of the invention, it will be apparent to those skilled in the art that numerous.

modifications and variations may be made in the form and construction thereof, without departing from the more fundamental principles of theinvention. I therefore desire, by the following claims, to include within the scope of my invention all such similar and modified forms of the apparatus disclosed, by which substantially the results of the invention may be obtained by substantially the same or equivalent means.

I claim:

1. In an electrical musical instrument for producing organ bass tones and having an amplifier and electroacoustic translating means, said instrument having a pedal clavier, the combination of two generating systems, each comprising an oscillator and a cascaded series of alternate pulse responsive frequency divider stages, a switch for each of the pedals of the clavier and respectively opened by the pedals, a relay for each pedal, circuits respectively completed by-the switches to energize associated relays, switch and circuit, means respectively rendered operative by the relays and efiective to tune one of said oscillators to a frequency related to the pitch of which the amplifier is normally ineffective to transmit the signals, and in which there is a means operable by any one of the pedal controlled relays to render the amplifier efiective to transmit the signals after the oscillators have been tuned by the relay controlled switch and.

circuit means.

3. In an electrical musical instrument for. pro-- ducing the pedal tones of an organ andcomprising an amplifier, the combination of a pedal clavier, a relay for each of the pedals. of said clavier, each of said relays being energized upon depression of its associated pedal and-operating three switches, a pair of oscillators, means controlled by the first of said relay switches to tune one of said oscillators to a frequency related to the pitch of the highest of a, plurality of depressed pedals, means operated by the second of said relay switches to tune the other oscillator to;

the frequency related to the pitch of the lowest of a plurality of depressed pedals, a circuit com pleted by the operation of the third relay switch to render th amplifier effective, a plurality of 13 cascaded alternate pulse responsive frequency divider stages connected to each of said oscillators, means for deriving from each of said divider stages output signals of different predetermined wave forms, and stop controlled relay operated switch means for selectively transmitting the output signals of said frequency divider stages to the amplifier.

4. In an electrical musical instrument including an amplifier for producing the pedal tones of an organ, the combination of a clavier comprising a plurality of pedals, a plurality of relays, each including three switches respectively operated upon depression of the pedals, a pair of oscillators, means controlled by the first of said switches to tune one of said oscillators to a frequency related to the pitch of the highest of a plurality of depressed pedals, means operated by the second of said switches to tune the other oscillator to the frequency related to the pitch of the lowest of a plurality of depressed pedals, a circuit completed by the operation of the third switch to render the amplifier efiective, a plurality of cascaded alternate pulse responsive frequency divider stages connected to each of said oscillators, means for deriving from each of said divider stages an output signal of predetermined wave form, and remotely controlled stop switch means for selectively transmitting the output signals of said frequency divider stages to the amplifier.

5. In an electrical generator of bass tones for a pipe organ having a pedal clavier and a shutter controlled swell box, the combination of a pair of oscillators capable of being tuned through a range of semitone intervals of extent as great as that of the pedal clavier of the organ, the pedal clavier of the organ comprising a plurality of pedals, a switch operable by each pedal, a plurality of relays respectively controlled by the pedal switches, means controlled by said relays for tuning one of said oscillators to a frequency related to the pitch of the highest pedal and tuning the other oscillator to a frequency related to the pitch of the lowest of two or more simultaneously depressed pedals, a multistage cascaded frequency divider system for each of said oscillators to provide frequencies which are submultiples of the frequencies respectively generated by said oscillator, an amplifying system for each frequency divider system, selectively operable remotely controlled means for coupling the various stages of each frequency divider system to its associated amplifying system, a loudspeaker for each amplifying system, said loudspeakers being located in the organ swell box,

and means operated by said relays for controlling the gain of both of the amplifying systems.

6. In an electrical musical instrument particularly adapted for supplementing the tonal output of a pipe organ equipped with a shutter control swell box by providing adequate bass tones, the combination of a pair of electronic oscillators, a pedal clavier comprising a plurality of pedals, means controlled by said pedals for tuning one of said oscillators to a frequency related to that of the highest of two or more simultaneously depressed pedals and tuning the other oscillator to a frequency related to that of the lowest of a plurality of simultaneously depressed pedals, a pair of multi-stage frequency dividers respectively coupled to said oscillators to successively divide by two the frequencies generated by the oscillators; two amplifying systems respectively associated with said frequency dividers, selectively operable means for coupling the outputs of predetermined stages of said frequency dividers to their respective amplifying systems, a pair of loudspeakers respectively coupled to said amplifying systems and located in the pipe organ swell chamber, and common means operated upon the depression of any one of the pedals to increase the gain of both of said amplifying systems.

7. In an electrical musical instrument having a bass tone generating system providing output signals of two different tone qualities, the first of the output signals comprising a fundamental frequency and a series of harmonics of high am plitude relative to the fundamental in which the peak amplitudes of the partials are substantially coincident, and the second signal comprising a fundamental frequency and relatively few harmonics of relatively low amplitude, an amplifying system, means for impressing the second signal directly upon the input of the amplifying system, and a frequency responsive phase distorting network forming a transmission line for impressing the first signal upon the amplifying system.

JOHN M. HANERT.

CES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,126,682 Hammond Aug. 9, 1938 2,233,258 Hammond et al. Feb. 25, 1941 2,332,076 Hammond et al. Oct. 19, 1943 2,233,948 Kock Mar. 4, 1941 

